A molecularly imprinted polymer undergoing a color change depending on the concentration of bisphenol A.

A molecularly imprinted system is introduced here whose color gradually changes as the analyte becomes rebound. The MIP was prepared from an acryloyl-modified β-cyclodextrin (β-CD), acrylamide (AAm), and N,N'-methylenebisacrylamide (MBAA), and imprinted with bisphenol A (BPA). The sensing capability of the MIP was first tested by potentiometry. A spin-coated gold plate coated with the MIP was used as a working electrode; the electrode can differentiate BPA from phenol or p-cresol, which were used as analogs of BPA. Next, a color-responsive system was fabricated by forming a hydrogel membrane containing the modified β-CD, AAm, and MBAA. A vesicle solution was prepared from N-(2-aminoethyl)pentacosa-10,12-diynamide by sonication and incorporated into the hydrogel. The blue polydiacetylene was formed by UV photopolymerization. In the presence of BPA, this system undergoes a color change from blue to red that is proportional to the degree of BPA rebinding. The color change is due to the contraction of the gel membrane that rebinding causes. The method works to 0.5 mM BPA concentration range. The detection limits for BPA are 0.1 mM on visual assessment and 50 μM on spectrophotometric readout. Graphical AbstractA molecular imprinting system is described whose color changes from blue to red as it binds bisphenol A. The degree of rebinding can be measured by detecting the color change of polydiacetylene vesicle. CD: cyclodextrin, BPA: bisphenol A.